DREAM
The Diffraction Resolved by Energy and Angle Measurements (DREAM) powder diffractometer is under construction at the European Spallation Source (ESS) as an in-kind contribution led by Forschungszentrum Jülich (Germany) in collaboration with Laboratoire Léon Brillouin (France) [1]. The project will be completed in 2025 with the end of cold commissioning.
The science case for the DREAM instrument is focused on the structure determination of complex materials with large unit cells, studies of new compounds with an interplay of magnetism and superconductivity, nanostructures, metal organic frameworks, thermoelectrics, hydrogen storage and catalysis materials. The capabilities of DREAM to perform fast in-situ and small sample measurements will serve the ever-growing needs of various scientific communities.
These capabilities are enabled by combination of thermal and cold fluxes in a bi-spectral instrument concept. The broad neutron bandwidth will include both thermal and cold neutrons at their peak intensities, providing at full detector coverage a Q-range of 0.01 – 25 Å–1 in a single frame, which is ideally suited for diffraction studies on multiple length scales.
The design of DREAM utilizes the long pulse and unpreceded peak brightness of ESS to provide a flexible choice between high resolution and high intensity. The estimated highest resolution in the backscattering detector is Δd ~ 0.0003Å will set a new world record in neutron diffraction. The pulse shaping chopper consisting of two fast counter-rotating disks will allow a seamless change between the high resolution and high intensity modes of operation.
The new 2D position sensitive 10B detectors will cover with high efficiency a large solid angle (initial coverage of 1.95 sr and 5.12 sr in the full coverage), and further enable neutron time-of-flight Laue single-crystal diffraction measurements. The full potential of DREAM will be realized through a new approach to the data analysis, which is based on 2D Rietveld refinements of the angular- and wavelength-dispersive diffraction data [2].
Simulations of 2D neutron diffraction pattern of Na2Ca3Al2F14 powder for DREAM instrument with complete detector coverage (left panel). The right panel shows resolution for various pulse widths.
DREAM Team:
Mikhail Feygenson, former project leader for DREAM, moved to ESS in July 2021 and has been the Head of the Diffraction and Imaging Division at ESS since February 2024. However, he is also affiliated with FZJ.
Forschungszentrum Jülich (DE): (Mikhail Feygenson), Werner Schweika, Peter Harbott, Andreas Poqué, Anja Schwaab
Laboratoire Léon Brillouin (FR): Florence Porcher, Sylvain Desert